Lawn Winterkill: Lessons from 2016-'17

Tony Koski' Extension Turf Specialist

It’s been a dry fall and early winter throughout most of Colorado – in spite of the recent snow (that’s rapidly disappearing as I write this today). Little precipitation, combined with windy, sunny, and warm days, is a pretty good recipe for some winter turf injury (aka “winterkill”). Throw in some alternating extreme cold with the warm days and things get potentially worse for turf, trees, and shrubs in our landscapes. But not all “winterkill” is the same when it comes to turf. Here are some examples from the spring of 2017 (these were all in April/May) to illustrate that point.

Winter injury from drought – enhanced by VERY thick thatch in this bluegrass lawn. Note that the green turf is where water was supplied by a gutter downspout, runoff from the driveway (plus the concrete acts as a “mulch” for turf growing alongside it), and runoff from the neighbor’s gravel-covered plastic.

This lawn had been sodded in early 2016 and was perfectly green and healthy going into the winter of

Dead area is where home construction had been "staged",
resulting in extreme soil compaction before sodding.

2016. It had been handwatered religiously throughout 2016, was mowed the correct height, and was otherwise perfectly cared for. The problem was the soil under the sod. The dead area was where home construction was “staged”: lumber, roofing, tile, other building supplies were dropped off – along with concentrated, heavy, constant traffic. The soil was not tilled sufficiently prior to sodding, so almost no rooting occurred following sodding. The constant handwatering in 2016 kept it alive and looking perfect, but the lack of rooting during the winter resulted in winter desiccation and sod death in spring 2017.

Sod had not rooted into the compacted soil, which
lead to winter kill in spring 2017.

Winter mite injury

This lawn suffered from turfgrass mite feeding in the late winter and early spring. Mite feeding and reproduction is favored by dry conditions. Drought-stressed turf is often killed by mite feeding in the spring if numbers are high enough and no snowcover or spring rains occur – and if winter watering isn’t performed at least a few times during the winter.

The common thread here? Water! Turf, trees, shrubs, and other landscape plants may not be growing and thus USING much water during the winter. But when it’s dry, windy, sunny, and humidity is low, our landscape plants are LOSING water. When we don’t receive enough snow to provide periods of snow cover during the winter, and plants aren’t mulched (like turf!), are young and not fully established, or have poorly developed root systems, winter watering can be essential for preventing winter injury or death.

When weather allows (above freezing for a day or two), run a hose and sprinkler out to the drier parts of your landscape (especially south- and west-facing parts of your landscape), to new sod, trees, and shrubs, and to areas where you have experienced winter injury in the past (perhaps from turf mites). Apply enough water to moisten the crowns of the turf plants and to get some water into the root zone of new trees and shrubs. The goal isn’t deep watering, but rather to prevent desiccation of crowns and young root systems.

The United States Botanic Garden Conservatory: Holiday Displays

Posted by: Yvette Henson, San Miguel County

For the 2014 Thanksgiving Holiday, my husband and I went to Washington DC to spend time with our youngest daughter who was doing an internship as part of her universities degree requirements.  While we were there we visited the US Botanic Gardens Conservatory.  https://www.usbg.gov/conservatory

In the conservatory Garden Court they had a display of Washington DC Landmarks made from all natural materials such as leaves, seeds, bark, fungi, etc.  I was totally blown away and forever inspired.  Here are pictures of a few of them.  (Keep in mind these pictures were taken with my iphone in 2014.)

US Capital

Lincoln Memorial

Smithsonian Castle

White House

2014 Garden Court Christmas Tree 

(surrounded by buildings made from all natural materials)

Just for fun I've included 2 photos from the Conservatory Model Train Display that was also part of the 2014 US Botanic Gardens  Conservatory holiday display.

Conservatory Model Train Track 

Fairy House 

I was so inspired by these beautiful displays that I started making fairy houses made of all natural materials with my granddaughter.  Ours don’t even approach the intricate detail of these made for display at our National Garden but they sure are fun! 

For more information on The Plant Based D.C. Landmarks at the United States Botanic Garden Conservatory go to this link  https://drive.google.com/file/d/1chs6NWIaO_Ha9_CvdKDUJXtuw2LXrET-/view 

This year the Conservatory is featuring a display of replicas of U.S. Roadside Attractions made out of all natural materials.  https://drive.google.com/file/d/1DKiLTvIiu16HFLecQCPjHIQrhL8f2AZW/view

Happy Holidays!

Leaf Musings

Posted by: Mary Small - State Master Gardener Coordinator

Leaves accumulating in front walk next to garage (r)

“I think that I shall never see a poem as lovely as a tree…” I reminded myself during a fall leaf cleanup. And yes, trees are wonderful, but I could do with a few less leaves in the front walk every year. The picture on the right greets me every couple of weeks during the fall months. Every fall.  It’s worse when the weather is windy. And lest you think the front steps are not affected -I swept them off before I thought to take the picture.

Instead of continuing to wonder why the neighborhood leaves end up in my front walk, I did a bit of research. Now, I’m not an engineer, but here’s what I understand. The wind hits the windward end of the garage and flows up over the roof and around the front (side) of the garage. Suction is created on the side wall of the garage and on the leeward side of the garage– which is where the front walk is located!
So that explains (at least in part) why leaves get “sucked into” the front walk. And it also explains why leaves get sucked into the garage when it's windy and the doors are open – like when you’re putting the car in it!




While cleaning up this batch of leaves, I wondered what species were filling up the walkway, since we only have one tree in the front yard. Digging through the pile I found about 10 different kinds of leaves.  Our tree could have been the source of the bur oak leaves (brown, far right). The nearest ornamental pear trees (bottom center) are 4 houses to the north and should have had plenty of opportunity to bother someone else before they arrived on my doorstep. There are numerous aspen (lower right, brown) across the street in at least 3 yards. The nearest cottonwood (upper left, brown) is at least three blocks away. I have no idea where the maple or red oak are located.

I next re-sorted the leaves. Look at the gorgeous anthocyanin pigments in the three beauties on the left and right.The pigments are present all year, but we only get to see them when chlorophyll – the green pigment- is no longer produced in the leaves. This happens in response to decreasing daylength and other factors as we approach fall.

Finally, I just had to put this mighty cottonwood leaf next to its more diminutive aspen relative.

I ended this work session thinking that tree leaves are really cool. (Remind me I said that in a couple weeks…)

Colorado State University Announces 2017 “Top Performing Perennials”

Posted by James E. Klett, 

Department of Horticulture and Landscape Architecture, Colorado State University

The following six perennials were recently selected by the Perennial Trial Garden sub-committee as being superior after 3 years of growth and winters.  Plan to utilize these in your designs and home gardens in 2018. I think you will be happy with the results.

Kahori® Border Pink from Bartels

(Dianthus ‘Kahori’)

Noted as an impressive advancement in breeding, evaluators described this as the new standard for Dianthus.  The vibrant pink flowers cover the plants at peak bloom and create a mat of stunning color.  This entry is superior for an extremely long period of bloom and exceptional uniformity.  It has proven to be reliably winter hardy and would look great in a rock garden or crevice garden.  It looks great in ground beds and would make a beautiful border, but is a great choice to use in containers since it is always in bloom.  This selection remains very compact and has great heat tolerance during the peak of summer temperatures.  It was very attractive even during its first year in the garden and has only gotten better each year since it was planted.

Winterbells® Helleborus from Hilverdakooij

(Helleborus Interspecific 'JWLS')

This winner was selected in part for its unique ability to bloom over the entire spring and summer.  It adds a touch of elegance to the garden with delicate nodding bells, glossy dark green foliage and a very attractive dense, compact growth habit.  Narrow, graceful foliage can be evergreen if planted in a protected location and is relatively low maintenance.  The subtly beautiful bell shaped flowers provide a long season of interest as they emerge a dusty pink, becoming pale yellow, white, and then light green by summer.  Besides making a great groundcover, the flowers are useful for cut flower production throughout the year.

 

 PHENOMENAL™ Lavender from Cultivaris

(Lavandula x intermedia ‘Niko’^PP24193)

The abundant, tall graceful flower stalks are held high above the foliage for maximum display.  Besides being very uniform, all plants had excellent cold hardiness.  It was noted that they would do best if grown on the drier side to avoid lodging of the flower stalks.  Pollinators are very attracted to this plant and it has a high oil content that makes is very attractive to commercial production as well as providing the classic lavender fragrance to the garden.

 

Flame® Blue Phlox from Bartels

(Phlox paniculata Flame^® Blue)

Abundant blue and white flowers are held upright on sturdy stems that never lodged despite overhead irrigation used in the garden.  Flower color is a subtle blue that is strongest in early summer and again late in the season as the temperature cools.  It was a relatively early bloomer starting in mid-July and could continue through October if deadheaded.  Self-branching plants had a very full and uniform growth habit as well as superior resistance to powdery mildew.

 

 

Ronica™ Dark Pink Veronica from Danziger

(Veronica Ronica™ Dark Pink)

Big, fat and sassy flower spikes put on an eye-catching show of vibrant pink flowers.  Plants keep a very formal appearance with great uniformity and glossy emerald green foliage that really sets off the pink flowers.  Bloom period was very long especially if deadheaded.  Had superior resistance to powdery mildew compared to other entries growing in the trial.  Growth habit was very full and dense.

 

Class of 2016 - “Too Good to Wait” Award

The Perennial Trial Garden Sub-committee likes to award the ‘Top Performer’ designation to superior plants that have been in the ground 2 winters and 3 growing seasons. This category is to acknowledge an upcoming plant that has been in the ground one winter and two growing seasons and shows excellent performance thus far in the trial. The following plant impressed the Perennial Trial Garden Sub-committee so much that they designated the category name: “Too Good to Wait Performer”.

 

KISMET™ Intense Orange Coneflower from Terra Nova Nurseries

(Echinacea 'TNECHKIO'^PPAF)

The sheer mass of vibrant flowers draws people all the way from across the street.  Prolific flowers form a solid canopy of blooms over the plants which makes this variety a great choice for the home gardener or landscaper looking for a showstopper.  The intense orange color almost seems to glow at its peak.  Flower color fades to an attractive shade of pale yellow to maintain a long season of bloom.  Foliage is also very unique and attractive early in the season.  Plants have a very uniform growth habit and good branching.  The KISMET™ series also features colors of raspberry, red and yellow.

Winter Water or Re-Sod, Your Choice

Posted by: Curtis Utley, Jefferson County Extension

Unless you have been living under a rock you will have noticed that

 we have been experiencing abnormally warm and dry weather

 this fall, and the long-range forecast looks to promise more

 of the same. In fact, NOAA reported: 

 
Native rocks which one could be proud to live under

...NOVEMBER 2017...DRIER AND MUCH WARMER THAN NORMAL...

AFTER AN OCTOBER WHICH EXPERIENCED A WIDE TEMPERATURE RANGE WITHIN

THE MONTH, NOVEMBER 2017 RECORDED A FAIRLY NARROW RANGE IN

TEMPERATURE DUE TO LACK OF EXTREME COLD. TWO DAILY HIGH TEMPERATURE

RECORDS WERE SET IN NOVEMBER. THE HIGH ON THE 26TH REACHED A RECORD

SETTING 74 DEGREES WITH 81 DEGREES REACHED ON THE 27TH. THE HIGH OF

81 DEGREES ON THE 27TH ALSO ESTABLISHED AN ALL TIME MONTHLY HIGH

TEMPERATURE RECORD FOR NOVEMBER. THE HIGH OF 81 DEGREES ON THE 27TH

EXCEED THE PREVIOUS MONTHLY HIGH TEMPERATURE OF 80 SET ON BOTH THE

6TH OF THE MONTH IN 2006 AND THE 16TH OF THE MONTH IN 2016.

AS FOR PRECIPITATION, NOVEMBER 2017 LANDED SHORT OF THE MONTHLY

AVERAGE AS PREDOMINANT STRONG WEST TO NORTHWESTERLY FLOW ALOFT

PROVIDED FOR FREQUENT BOUTS OF DRY DOWNSLOPE FLOW ALONG THE NORTHERN

FRONT RANGE. A FEW WEAK COLD FRONTS PUSHED THEIR WAY INTO NORTHEAST

COLORADO DURING THE MONTH, HOWEVER WITH LIMITED MOISTURE ASSOCIATED

WITH EACH ONE, ONLY LIGHT PRECIPITATION AMOUNTS WERE RECORDED. A

STRONG AND FAST-MOVING DISTURBANCE, WHICH PASSED ACROSS SOUTHERN

WYOMING AND NORTHERN COLORADO LATE IN THE DAY OF THE 17TH, PUSHED

RAIN SHOWERS ONTO THE LOWER ELEVATIONS AND GAVE DENVER THE HIGHEST

PRECIPITATION FOR THE MONTH WITH 0.23 ON THE 17TH.

AS THE THANKSGIVING HOLIDAY APPROACHED, A LARGE RIDGE OF STABLE HIGH

PRESSURE BEGAN TO DEVELOP OVER THE SOUTHWEST UNITED STATES ON THE

21ST. THIS STABLE RIDGE PERSISTED ACROSS THANKSGIVING AND INTO THE

NEXT WEEK WHILE KEEPING THE REGION AND DRY WITH WELL ABOVE AVERAGE

AND EVEN RECORD SETTING TEMPERATURES.

TEMPERATURES:

THE AVERAGE TEMPERATURE AT DENVER INTERNATIONAL AIRPORT FOR THE

MONTH WAS 45.3 DEGREES F, WHICH IS 7.0 DEGREES ABOVE NORMAL. THIS

NOW RANKS AS 10TH WARMEST NOVEMBER`S SINCE TEMPERATURES RECORDS

BEGAN IN 2017 1872. THE WARMEST NOVEMBER ON RECORD OCCURRED IN 1949

WITH AN AVERAGE MONTHLY TEMPERATURE OF 50.9 DEGREES F. THE COLDEST

NOVEMBER ON RECORD WAS OCCURRED IN 1880 WITH A MONTHLY AVERGAE OF

22.0 DEGREES.

TEN WARMEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

50.9 1950

47.2 1999

46.2 1933, 1914

45.9 1981, 1927

45.6 1910, 1917

45.5 1917

45.3 2017

TEN COLDEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

22.0 1880

28.9 2000

29.7 1985

31.5 1929

32.3 1952

32.5 1889

32.8 1972

33.0 1886

33.1 1872

33.3 1979

PRECIPITATION:

PRECIPITATION FOR THE MONTH OF NOVEMBER AT DENVER INTERNATIONAL

AIRPORT WAS 0.29 INCHES, WHICH IS 0.32 INCHES BELOW THE NORMAL OF

0.61 INCHES. THERE WERE 3 DAYS WITH MEASURABLE PRECIPITATION DURING

THE MONTH. 0.23 INCHES OF PRECIPITATION FELL ON THE 17TH, WHICH IS

THE GREATEST DAILY AMOUNT FOR THE MONTH.

TEN WETTEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

3.21 INCHES 1946

2.67 INCHES 1991

2.63 INCHES 1983

2.13 INCHES 2015

1.95 INCHES 1922

1.93 INCHES 1886

1.88 INCHES 1975

1.74 INCHES 1908

1.69 INCHES 1972

1.68 INCHES 1881

TEN DRIEST NOVEMBER`S IN DENVER WEATHER HISTORY SINCE 1872:

TRACE 1949, 1901, 1889

0.01 INCHES 1939

0.03 INCHES 1917

0.04 INCHES 1905, 1904

0.05 INCHES 2003

0.07 INCHES 1903

0.08 INCHES 1920, 1874

NO THUNDER WAS OBSERVED AT DENVER INTERNATIONAL AIRPORT AND

4 DAYS WITH DENSE FOG WITH A VISIBILITY AT OR BELOW 1/4 MILE DURING

THE MONTH. THE PEAK WIND GUST OF 52 MPH FROM THE NORTHWEST OCCURRED

ON THE 1ST.

While attending the Rocky Mountain Regional Turfgrass Association Conference and Trade Show last week my colleague, Carol O’Meara and I were lamenting the fact that landscapes along the Front Range are going to suffer if the dry warm weather continues through the winter. Both of us planned on watering our landscapes a little, over the weekend, to prevent winter-kill from desiccation.

I also received a few calls last week from landscape maintenance companies concerned about protecting customer’s lawns from turfgrass mites which can kill drought-stressed turf in the winter months. This morning I decided to inspect the turfgrass outside of my office for mite activity and sure enough, I found clover mites actively feeding on the turf close to a south-facing retaining wall. Without natural winter precipitation or winter watering it is likely the clover mite population will explode and cause enough feeding damage to the quasi dormant turf to kill it out right.

Southwest facing retaining wall

Active Clover mites

Clover mites and Bank’s grass mites are cool-season pests of turfgrass along the Front Range and have caused economic damage to landscapes in the past and will kill turf this year too unless susceptible aspects of lawns receive irrigation or natural precipitation. To learn more about turf mites, check out the factsheet http://extension.colostate.edu/docs/pubs/insect/05505.pdf   

What does that mean? Damage caused by these cool-season mites is always most severe on south or west facing slopes (aspects) or on the South or West sides of evergreen trees, shrubs, buildings, walls, and fences, so focus your winter watering efforts on those areas of your lawn specifically. To learn more about winter watering, check out the factsheet  http://extension.colostate.edu/docs/pubs/garden/07211.pdf

South facing slope with mite damage

South facing side of a blue spruce

West facing slope with mite damage

Check for mite activity in your lawn by swiping a white sheet of paper over the lawn. Turn the paper over and examine it for small red streaks; the streaks represent crushed mites. If found, know that your lawn at that specific location is in peril and you should water. If the paper has lots of streaks, consider spraying that aspect with an insecticidal soap to knock back the population of mites then begin watering. To learn how to check for mites, watch this video

Next spring, if you notice the south and west aspects of your lawn are not greening-up with the rest of your lawn, check the margins of the damage with a clean sheet of white paper. If you find streaks, begin watering.The areas of turf that have not greened up by April are probably dead and should be re--sodded, reseeded or, consider mulching those areas and planting western natives in those locations. To learn more, check out this factsheet http://extension.colostate.edu/docs/pubs/garden/07241.pdf  or this Plantalk script http://planttalk.colostate.edu/topics/lawns/1517-sodding-lawn/ . A little water now may save you the cost of replanting, and a lot of water next spring to re-establish your turf.

Small red streaks are crushed mite bodies and indicate activity

City Trees versus Country Trees

Posted by: Alison O'Connor, Larimer County Extension

Remember the book "Town Mouse Country Mouse" by Jan Brett? It was one of my favorites growing up. The plot was simple: a mouse from the country and a mouse from town swap lives and homes...and adventures follow!

Book cover from Amazon.com

An article from "Scientific Reports" from nature.com (published in November 2017; https://www.nature.com/articles/s41598-017-14831-w) reminded me of this story--but it focused on city (urban) trees and country (rural) trees and how they've differed in growth since the 1960s.

There's been a lot of research on how climate change (warming temperatures, increase carbon dioxide, longer growing seasons) have affected trees in the forest, but little research has looked at trees in urban areas. In general, warmer temperatures and increased carbon is good for trees. Carbon is used in the process of photosynthesis and warmer temperatures make photosynthesis more productive (to a point). City trees, compared to rural trees, often live among warmer temperatures (due to increased infrastructure and people) and increased carbon levels (due to pollution and industry).

Photo courtesy of Portland State University.

And yes, it comes down to climate change. But instead of getting political, let's just discuss the study and what they found.

The study looked at trees in 10 metropolises worldwide: Sappora, Japan; Price George, Canada; Berlin, Germany; Munich, Germany; Paris, France; Santiago de Chile, Chile; Cape Town, South Africa; Hanoi, Vietnam; Brisbane, Australia; and Houston, Texas. These cities differ in latitude, mean annual precipitation, mean annual temperature and climate zone (ranging from boreal to subtropical). The purpose was to determine how climate change and the urban heat island effect affect the vitality and growth of urban plants.

Metropolis locations for the research study.

The study looked at nearly 1400 mature trees of varying species: Sachalin fir, spruce, littleleaf linden, horsechestnut, London planetree, black locust, English oak, African mahogany, hoope pine and water oak. The data collected took two cores of the trees (from the north and east) and measurements like diameter at breast height (DBH), height and height to crown base. From these measurements, the researchers developed equations to test for overall growth trend and overall urban zone effect. And the researchers also wanted to get more detail about the combined effects of urban zone affiliation and period-specific growth trends, translating this across climate zones. Phew!

To sum it up (if you want to stop reading here): City trees grew better, overall, compared to their rural counterparts and climate change increases growth for city trees. But, this increased growth may lead to shorter overall lifespans and more rapid aging.

Since 1960, the study found that overall tree growth (in both urban and country locations) has increased. The study also found that urban trees will be larger and reach a greater size than a rural tree of the same age. But as the trees grow older (100+ years), the growth rate decreases for city trees, resulting in urban trees that are only 18% larger than rural trees after 100 years.

It also varies by climate zone. Colorado would likely be classified as a "temperate" climate and the research found that urban trees in this climate (in the cities of Paris, Berlin and Munich) grew significantly slower than rural trees. This was the only climate where urban trees were found to grow more slowly.

The City of Fort Collins

As urbanization continues and more people gravitate to living in urban areas, having trees in these areas becomes of utmost importance. I don't need to belabor the benefits of trees, but they do a lot for our local communities, climate and overall well-being. Interestingly, this study found similar results to what is being found in forest regions--accelerated growth (studies conducted in central Europe and Japan).

Another major thing the study didn't specifically address, but something Coloradans should have on the forefront of our minds is water and drought. While increasing temperatures can mean accelerated growth for trees, it cannot happen if there is drought or water shortages. As a result, drought will reduce growth and/or contribute to tree death. Urban trees can suffer from water stress due to higher temperatures and modified precipitation patterns...along with unfavorable soil conditions (compaction, impervious surfaces, etc.).

Boy, don't I feel like a downer! In short, studies like this one can open our eyes to the effects of climate and how trees respond in urban areas. It really is interesting...and my only advice to you is to plant your trees properly, select the correct species and care for and maintain them as best you can. Celebrate trees in our communities!

Town Mouse meets Country Mouse

Landscaping with Colorado Native Plants Conference

Landscaping with Colorado Native Plants Conference

February 10, 2018 at the Denver Botanic Gardens

Registration for the 3rd Annual LWCNP Conference NOW OPEN! landscapingwithcoloradonativeplants.wordpress.com.

Our keynote speaker will be Panayoti Kelaidis: Native Plants in the Garden: a Problem or Panacea?

This talk will present a few of the challenges encountered establishing native plants at Denver Botanic Gardens (and similar institutions) such as the difficulty of procuring germplasm, how hard they can be to establish and maintain and the often negative reaction to poorly designed native plantings. Panayoti will then show solutions to each of these challenges that intelligent design and proper maintenance can obviate: a successfully established native garden can be a panacea in our urban spaces—minimizing irrigation and runoff and reaffirming our connection to Nature in every sense.

Topics for the ‘New to natives’ breakout session will include planting for habitat, planting for year-round interest, adding natives to an existing landscape (including replacing your lawn), and “plant this, not that”.  Topics for the ‘Knows the natives’ breakout sessions will include maintenance,  rock/crevice gardening (including bare-root planting), soils for native plants, and water conservation through passive water harvesting.  We will end the day with panel with a grower’s perspective on natives.

We will also have many wonderful vendors to check out before and after the conference, and during breaks.

The Landscaping with Colorado Native Plants Conference promotes the inclusion of native plants in our landscaping to benefit pollinators and songbirds, save water, and restore the beauty and health of nature in the places we live, work and play. 

While we recommend the use of straight species and local ecotypes wherever possible, we support the use of varieties and cultivars of native species as long as their breeding doesn’t interfere with their ability to function in nature and maintain key relationships with pollinators and other lives.